Derby's 50-year-old flood defences are being tested over the next few months amid concerns they could be reaching the end of their life.
Test drillings will take place along the banks of the River Derwent.
More than 30 exploratory bore holes will examine soil and rock samples for analysis to determine the integrity and suitability of existing flood defences.
The agency said it would analyse the results and consult widely before taking decisions on any future work.
Project Manager Tim Ive, said: "It's only common sense to make sure the defences are up to the task we might ask of them.
"The very latest hydraulic modelling techniques coupled with known historical information about previous flooding in Derby will provide a far more accurate picture of the extent and likelihood of any future flooding."